textproduct: Albany

WHAT HAS CHANGED

Similar to the previous forecaster, lowered temperatures across the mid-Hudson Valley, NW CT and the eastern Catskills due to expected evaporative cooling due to ongoing steady precipitation and clouds. The decreased temperatures in the eastern Catskills continues to favor a rain/snow mix this afternoon turning to mainly wet snow for a period tonight above 2000ft tonight. There is now a low to medium chance for light snow accumulations (mainly under 1 inch) for elevations at and above 2000 feet.

We again leaned towards the lower end of the blended guidance for dew points during peak heating hours both Monday and Tuesday afternoon. With an increasing pressure gradient, we also increased winds and gusts for Tuesday afternoon. There is now a low chance that relative humidity values and winds will near critical fire weather conditions on Tuesday.

KEY MESSAGES

1) While widespread rain will impact the western Mohawk Valley, northern/eastern Catskills, Mid-Hudson Valley, central and southern Taconics and Litchfield County today into tonight, no flooding impacts are anticipated.

2) Drier weather returns to start the upcoming week with a medium chance that relative humidity and winds reach near critical fire weather levels on Tuesday.

DISCUSSION

KEY MESSAGE 1...

A weak sfc low in western PA will track southeastward today along a stationary boundary positioned in the mid-Atlantic. High pressure parked in eastern New England today and strong confluent northwesterly flow over the Northeast advecting dry air aloft will supply plenty of dry air to areas north of I-90 resulting in a sharp moisture gradient from south to north. Latest water vapor imagery including the Advected Layer Precipitable Water (ALPW) show distinct moisture fetches from the western Atlantic and from the Gulf getting stretched along the axis of dilatation just north of the boundary. This has led to a region of enhanced mid-level FGEN and a swath of widespread steady rain positioned across southern NY and eastern PA extending into eastern CT and NYC/Long Island. Drier air closer to I-90 as noted on the 12 UTC ALY sounding continues to erode the precipitation shield as it tries to build northward. This will lead to a sharp south to north rainfall gradient between I-90 and the mid- Hudson Valley/eastern Catskills and NW CT through tonight.

The highest forecast uncertainty in our rainfall forecast today/tonight lies closer to I-90 where the northern edge of the rain has hit the brakes. While the I-90 corridor and especially areas to the north will remain dry through much of the afternoon, PoPs trend upwards to low end chance (30 - 50%) by 21 UTC near I-90 and remain in the chance category through almost Midnight as the parent shortwave moves overhead. Areas in the southwest Adirondacks, Glens Falls/Lake George Region and most of southern VT have the lightest chance to remain mainly dry through tonight. On the other hand, there is medium to high confidence that at least 0.75" of precipitation will fall in the mid-Hudson Valley, eastern Catskills, and NW CT in the 24hour period ending 12 UTC Sunday; however, no flooding is expected. Evaporative cooling will keep temperatures much cooler south of I-90 where temperatures will stay stuck in the 40s the rest of the day with even low to mid 30s for elevations 2000ft and higher in the eastern Catskills supporting a rain/snow mix this afternoon and a period of wet snow tonight. However, marginal temperatures will limit wet snow accumulations with the latest NBM probabilistic guidance showing just a 30 to 50% chance for amounts to exceed 1" at elevations 2000ft+ and mainly under a 25% chance to exceed 2". Further north, a thinner cloud canopy will allow temperatures to warm into the low to mid 50s. The steadiest rain departs from west to east after Midnight with a dry and spring-like conditions returning for Sunday.

KEY MESSAGE 2...

Subsidence builds over the Northeast Sunday through Tuesday in response to an amplifying ridge shifting eastward out of the Ohio Valley. This will keep us very dry each day with deep boundary layer mixing trending relative humidity values downwards each afternoon. Forecast soundings show a potential "dew point" bomb on Monday as the ridge axis remains to our west and limits much of a subsidence inversion. Given this plus sunny skies, we used NBM10th percentile guidance for Monday P.M dew points to highlight low RH values, similar to the previous forecast. While the subsidence inversion returns on Tuesday, forecast guidance continues to support dry air advection, deep mixing leading to warmer temperatures, and breezier winds with gusts up to 25mph due to a tightening pressure gradient. Therefore, we again used NBM10th guidance for dew points to relay low RH values. While there is medium to high confidence that both Monday and Tuesday will feature RH values in the 25 to 35% range across eastern NY and western New England, breezier winds on Tuesday has increased confidence in reaching near critical fire weather conditions, especially near/north of I-90 which will miss out on the widespread rain today/tonight. We will consult our fire weather partners early this week to learn if fuels are available for fire spread and decide if we need to message weather conditions that can enhance fire spread.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through 18z Sunday...VFR conditions prevail across all TAF sites this afternoon as an axis of steady rain stalls mostly to the west. POU, currently observing rain, is the only site that has gotten any thus far today, but the light rates have allowed visibility to remain unaffected.

As the lower levels continue to moisten and the rain shield to push farther east, conditions should gradually worsen into MVFR thresholds, primarily through ceiling heights. GFL is the exception to this as the southeast propagation of the rain shield should keep the greater moisture to the south and maintain VFR conditions here throughout the 18z cycle. But once the causing low departs off the Mid-Atlantic Coast early tomorrow morning, rain will taper off and MVFR conditions at ALB, POU, and PSF should gradually improve back to VFR by the end of the period. Winds will prevail out of the south to southeast to begin the period, generally at sustained speeds under 10 kt. The exception is the occasional stronger wind at ALB where sustained speeds could reach up to 15 kt with gusts of about 20 kt. By the end of the period, winds shift to the east and northeast but will remain light with sustained speeds under 10 kt.

Outlook...

Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Low Operational Impact. Breezy. NO SIG WX. Tuesday Night: Low Operational Impact. Slight Chance of SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA. Wednesday Night: High Operational Impact. Likely SHRA. Thursday: Moderate Operational Impact. Breezy. Chance of SHRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.